1. Field of the Invention
This invention relates to apparatus and methods for precisely locating originals affixed onto an original-holding cylindrical drum of an input scanning unit of a drum type image scanning apparatus such as a color scanner for use in graphic arts and, more particularly, to a device by which an operator can position the originals exactly and easily on the drum either parallel with the axis of the drum or oriented at a specified angle thereto.
2. Description of the Prior Art
In a conventional drum type image scanning apparatus, a transparent cylindrical drum in the input scanning unit serves as a base onto which is wrapped the "original" to be scanned. The original is fastened on with an adhesive tape and the drum is rotated at a controlled speed so that the fastened original is optically scanned by means of a photoelectric scanning head which is transversely fed (crossfed) while facing the drum. The original is attached to the drum either while the drum is in the image scanning apparatus or while it is detached therefrom. In this operation, a line serving as a reference is not provided on the original cylinder, because if such a reference line were on the original cylinder itself, a shadow produced thereby would negatively affect the scanning process. Accordingly, in the process of attaching the original to the drum, the original is usually oriented either in parallel with the axis of the original cylinder, or at a specified angle therewith, based solely on the perception and judgment of the operator.
The applicant has already proposed one solution, disclosed in Japanese patent application No. 58-72679, wherein, by using a projector for projecting a focused image while continuously changing the projection magnification, an image of the original is projected on a block copy layout sheet to coincide a contour of the projected image with that of an image drawn on the layout sheet. This allows simultaneous realization of the reproducing magnification of the original and a predetermined angle between the projected image of the original and the image of the block copy. Keeping its particular orientation, each original is individually affixed to a transparent sheet so that, for each transparent sheet, an original is affixed onto the scanner drum.
However, there is still present the disadvantage of increased cost, since such an original patching device is in effect a highly accurate enlarger and it is necessary to have a transparent sheet for each original. Even with such expensive devices using transparent sheets, the patching operation must still be based largely on the perception and skill of the operator, and the desired accuracy is not always obtained.
Arguably, with a conventional scanner in which each original is individually scanned, strict accuracy is not required in orienting the original on the drum, and reliance on the operator's judgment may suffice.
However, in using a composing scanner for reducing or enlarging the original picture which is scanned and recorded at a specified position or in case of a layout scanner which performs various image processing operations such as masking, to shorten and simplify the image processing operation it is indispensable to accurately orient and affix each original to the scanner drum.